Conventional multi-needle embroidery sewing machine is capable of consecutive executions of embroidery sewing operations with multiple thread colors. Such multi-needle embroidery sewing machine has a needle-bar case containing six needle bars, for instance, provided at the extremity of its arm. The required needle bar is selected from the needle bars contained in the needle-bar case by moving the needle-bar case in the left and right direction. The selected needle bar is thereafter connected to the needle-bar drive mechanism and driven up and down to execute the sewing operation.
The controller of the sewing machine receives input of pattern data that contains instructions on stitch-by-stitch needle drop point, which determines the movement amount of workpiece cloth, and timing for changing the thread color, etc. Based on the pattern data, the controller transfers the embroidery frame holding the workpiece cloth in the X and Y directions by the transfer mechanism while controlling the needle-bar drive mechanism and other drive mechanisms to form embroidery in multiple colors.
Recent developments in the above described multi-needle embroidery sewing machine is provision of a decoration feature for decorating a cloth using a method called needle punching. To elaborate, some of the needle bars mount a needle punch needle in place of an ordinary sewing needle for needle punching the workpiece cloth based on needle punch information.
A recent example of such feature is realized, for instance, by a puncher applying a dot impact printer that creates accessories and furnishings by punch engraving desired pictures, illustrations, and characters on objects such as plastic or metal plates and wooden or fiber-made boards with a punch needle. The puncher is configured to create a predetermined punch engraving on the surface of the workpiece by transferring the printer head provided with a plurality of punch needles in the X direction while transferring the workpiece in the Y direction.
Such feature of the puncher may be implemented on the above described multi-needle embroidery sewing machine by attaching a punch needle on some of the needle bars in place of a sewing needle. In such case, because the punch needle is designed to only impact the surface of the workpiece, it needs to be dimensioned in shorter length as compared to a sewing needle that penetrates the workpiece cloth. Further, a holder for holding the workpiece in place is attached to the carriage of the transfer mechanism instead of an embroidery frame for holding the workpiece cloth. The desired punch engraving can be formed on the surface of the workpiece by moving the workpiece based on punch data and driving the needle bar mounted with the punch needle up and down.
The challenges encountered in generating the punch data required for execution of a punch engraving operation by the embroidery sewing machine is how to generate the punch data for executing the punch engraving operations for creating multiple patterns that are aligned especially in the lateral direction. Because the conventional punchers apply dot impact printers in their primary structure, the punch engraving operation is executed by transferring the workpiece, that is, the base, pitch-by-pitch in the front and rear direction corresponding to the direction of feeding sheets while reciprocating the head provided with the punch needle in the lateral direction, or the printing direction, orthogonal to the sheet feeding direction. In summary, a row of punch engraving operation is executed in the lateral direction as similarly done in the case of printing a sheet of paper, whereafter the row is updated to the next row and another line of punch engraving operation is executed and the process repeats itself thereafter.
For example, suppose the user intends to create a pattern P shown in FIG. 9B made of multiple characters aligned in horizontally that reads “WELCOME”. In the conventional punchers, the punch needle or the head is transferred laterally relative to the workpiece from arrow a, arrow b, arrow c, arrow d, arrow e, arrow f, and arrow g in the listed sequence to punch engrave the black portions, that is, the lower portions of each character pattern P. Next, the row is updated by moving up a row in the front and rear direction by a single pitch to punch engrave the next and subsequent rows.
However, when the above described punch sequence is employed in punch engraving operation by the embroiderable sewing machine, the following problem is encountered. When a sizable blank space lies between the neighboring patterns, the punch needle needs to stop its up and down movement while the punch needle is relatively moved over the blank area, meaning that considerable time is wasted in unproductive or empty transfers.